The present invention relates to a spring retainer for a clutch piston for use in a hydraulic clutch of an automatic transmission.
Referring to FIG. 3, a hydraulic clutch of an automatic transmission includes a clutch drum 2 formed with a ring cylinder 3, and a piston 4 slidably disposed in the cylinder 3 for pressing friction plates 9 splined to the clutch drum 2. A dish spring 6 is arranged for a return operation of the piston 4, and has a position restricted by a spring retainer 7 which is prevented from falling away by a snap spring 8 engaged with a cylindrical shank 5 extending from an inside diameter portion of the cylinder 3. The spring retainer 7 is in the form of a ring having a rectangular section obtained by a machining, and has an end face which abuts on an end face of the snap ring 8 to thereby be prevented from falling away. A constitution of such hydraulic clutch is disclosed, for example, in JP-U 2-128828.
When the dish spring 6 undergoes a force due to a displacement of the piston 4, this force is applied to the snap spring 8 through the spring retainer 7. Referring to FIG. 4, with such prior art constitution for a positional restriction by the spring retainer 7, however, since an inside diameter portion of the snap ring 8 is engaged with a snap ring groove 10 and fails to be movable, only an outside diameter portion thereof is urged to move in the axial direction and tends to trip as indicated by an arrow X. The spring retainer 7 which undergoes a force P also tends to trip in the same direction as that of the snap ring 8, i.e. as indicated by an arrow Y.
As a result, the snap ring 8 also undergoes a force at an outside diameter edge portion 8a thereof, resulting in a further increase in a bending moment. Additionally, if an offset "h" is found between an inside diameter edge of the dish spring 8 and an outside diameter edge of the snap spring 8, tripping is further increased. Thus, an irregular load operates on the snap ring 8 every engagement/disengagement of the clutch, producing a gouge and/or a wear on the snap ring 8 and/or the snap ring groove 10, resulting in an easy omission of the snap ring 8.
Further, since the spring retainer 7 has a simple rectangular section, an inside diameter edge thereof is easy to catch in the snap ring groove 10 or to be fitted therein upon assembling work, resulting in a difficulty in both manual assembling and automation of an assembling process. Furthermore, the spring retainer 7 is formed by a machining, increasing a manufacturing cost.
It is, therefore, an object of the present invention to provide a spring retainer for a clutch piston which is easy to assemble without any possible omission, and low in a manufacturing cost.